Crosslinkable composition of matter-IV

ABSTRACT

A novel, self-crosslinkable polydiene-functionalized polydieneophile-functionalized epoxy-amine adduct is disclosed, which self-crosslinkable epoxy-amine adduct is cureable at elevated temperature. The polydiene-functionalized polydieneophile-functionalized epoxy-amine adduct is the reaction product of polyhydroxy functional epoxy-amine reactant with preferably approximately equal molar equivalent amounts of diene functional mono-isocyanate and dieneophile functional mono-isocyanate. The self-crosslinkable epoxy-amine adduct is useful in coating compositions and like applications and is especially useful in cathodic electrocoating compositions and processes.

TECHNICAL FIELD

This invention relates to certain novel self-crosslinkable epoxy-amineadducts and to compositions of matter comprising same. Moreparticularly, the invention relates to diene-functionalizeddieneophile-functionalized epoxy-amine adducts, which are interreactiveat elevated cure temperatures. This invention further relates to the useof such self-crosslinkable epoxy-amine adducts in coating compositionsto prevent corrosion of corrosion susceptible substrates such as ferrismetal substrates and the like. Particularly in this regard, theinvention relates to aqueous coating compositions comprising suchself-crosslinking epoxy-amine adducts, which aqueous coatingcompositions are adapted for use in cathodic electrodepositionprocesses.

RELATED APPLICATIONS

This application is related to concurrently filed application Ser. No.455,678, 455,719, now U.S. Pat. No. 4,486,571, 456,067, 456,068 and458,119, now U.S. Pat. No. 4,508,879.

BACKGROUND ART

Coating compositions are known which are suitable for application to asubstrate, for example, by spraying, dipping, electrodeposition or thelike, which coating compositions are then cured by baking the coatedsubstrate at an elevated temperature. Typically, such coatingcompositions comprise resinous materials or blends of resinousmaterials, in some cases together with suitable crosslinking agentreactive with such resinous materials at elevated temperature.

In regard to electrodeposition of coatings, the process is welldescribed in the art. Typically, an aqueous bath containing the coatingcomposition is placed in contact with an electrically conductive anodeand an electrically conductive cathode, and upon the passage of electriccurrent (normally direct current) between the anode and the cathode, anadherent film of the coating composition is deposited. Depending uponthe nature of the coating composition, the coating may be deposited atthe anode or at the cathode. The process parameters vary widely. Thevoltage applied may vary from as low as, for example, one volt to ashigh as, for example, 500 volts or higher. Typically, however, thevoltage used ranges from about 50 to about 400 volts.

A wide variety of electrodepositable resins are known to the skilled ofthe art. For example, a number of water-soluble, water-dispersable, orwater-emulsifiable polycarboxylic acid resins can be electrodeposited.Some of these resins include, for example, reaction products or adductsof a drying oil or semi-drying oil fatty acid ester with a dicarboxylicacid or anhydride; interpolymers of a hydroxyalkyl ester of anunsaturated carboxylic acid, unsaturated carboxylic acid, and at leastone other ethylenically unsaturated monomer; alkyd-amine vehicles, thatis vehicles containing an alkyd resin and an amine-aldehyde resin; andmixed esters of resinous polyols. In U.S. Pat. No. 3,991,028 to Irwin etal, electrodepositable compositions are disclosed which comprise awater-dispersion of a hydrolyzed polyepoxide in combination with aninterpolymer of a hydroxyalkyl ester, an unsaturated acid and at leastone other monomer, and an amine-aldehyde resin. The use of a hydrolyzedpolyepoxide is said to provide improved properties and to avoidagglomeration of the coating composition. In U.S. Pat. No. 4,026,855 toParekh et al, a coating composition is disclosed to be adaptable for usein electrodeposition or as a water-based coating for application byspray or dip coating methods. The composition comprises an aqueousdispersion of (A) an ungelled modified crosslinking agent comprisingcertain aminoplast crosslinking agent modified by reaction with anon-resinous compound containing hydroxyl-group containing carboxylicacid, and (B) a water-dispersable non-gelled polymeric material carryinga cationic charge and containing at least one class of reactive groupsselected from carboxyl groups, alcoholic hydroxy groups and amide groupsand also containing amino groups, and (C) an acid solubilizer. In U.S.Pat. No. 4,033,917 to Sekmakas et al, certain copolymers ofpolyethylenically unsaturated epoxy-amine adducts are disclosed and alsostable aqueous dispersions containing same and also theelectrodeposition of such aqueous dispersions at the cathode of aunidirectional electrical system. Specifically, amine functionalpolymers dispersable in water with the aid of a solublizing acid aresaid to be provided by copolymerizing (A) certain ethylenicallyunsaturated hydroxy functional amine adduct free of epoxy groups; and(B) copolymerizable monoethylenically unsaturated monomers, a portion ofwhich is amine-functional. The copolymer is said to be stablydispersable in water at certain pH and to be electrodepositable at thecathode, optionally together with an aminoplast curing agent to providecoatings which can be cured, usually by exposure to elevatedtemperature. U.S. Pat. No. 3,471,388 to Koral is directed to a cathodicelectrocoating composition which incorporates an aminoplast crosslinker(e.g., butylated melamine) with an aminated polymer containing hydroxygroups. Numerous suitable hydroxy-containing aminated polymers aresuggested which have capability to crosslink with an aminoplastcrosslinking agent. One such suggested polymer is the reaction productof a poly-functional amine with a poly-functional epoxy compound. Thepolyhydroxy polymers are said to be disperable in water upon addition ofsuitable acid such as acetic acid.

Additional teaching directed to coating compositions suitable for use inelectrocoating processes is provided in U.S. Pat. No. 4,159,233 to Tingeet al; U.S. Pat. No. 4,057,523 to Blank; U.S. Pat. No. 4,182,831 toHicks; U.S. Pat. No. 4,192,932 to Dickie, which patent is assigned tothe assignee of the present application; U.S. Pat. No. 4,192,929 toBloomfield, which patent is assigned to the assignee of the presentapplication; U.S. Pat. No. 4,202,746 to Lee et al; and U.S. Pat. No.4,072,536 to Otsuki et al.

It is a general objective of the present invention to provide certainself-crosslinkable epoxy-amine adduct adaptable for use in coatingcompositions, including coating compositions adapted for use inelectrodeposition processes, and also for use in the manufacture of lowpressure laminates, adhesives, molding compounds and textile treatingresins. It is a further objective of the invention to providesolvent-based coating compositions and water-based coating compositionsapplicable to a substrate by spray or dip coating or the like.

One particular objective of the invention is to provide aself-crosslinkable coating composition comprising an aqueous dispersionof self-crosslinkable epoxy-amine adduct, which coating composition isadapted for use in the electrodeposition of coatings onto electricallyconductive substrates, in particular, self-crosslinkable coatingcompositions adapted for use in the cathodic electrodeposition ofcoatings, especially corrosion resistent primer coatings on automotivevehicle body panels. Additional objects and aspects of the presentinvention will be apparent from the following description thereof.

DISCLOSURE OF THE INVENTION

The present invention provides a novel substantially gel-freeself-crosslinkable epoxy-amine adduct, preferably of number averagemolecular weight about 500-8000, comprising the reaction product of (i)polyhydroxy functional epoxy-amine reactant comprising the reactionproduct of polyepoxy reactant having an average of at least about 2epoxy groups per molecule with secondary amine reactant having a totalof less than about 20 carbons per amino nitrogen, wherein each hydroxygroup, if any, of the secondary amine is removed at least 1 carbon fromeach amino nitrogen with (ii) diene functional mono-isocyanate reactantand with (iii) dieneophile functional mono-isocyanate reactant.

The self-crosslinkable epoxy-amine adduct of the invention isparticularly useful in coating compositions and according to onepreferred embodiment further discussed below can be adapted for use inelectrodeposition coating processes. Crosslinkable compositions providedby the invention may also be used in the manufacture of low pressurelaminates, adhesives, molding compounds and textile treating resins.According to a significantly advantageous aspect of the invention, thecure rate and storage stability of compositions comprising theself-crosslinkable, heat curable expoxy-amine adducts is readilycontrollable as further described below through selection of suitablediene and dieneophile resin moieties. In addition, the crosslink densityin the cured composition can be easily and precisely controlled bysuitable selection of epoxy-amine resin or by varying the stoichiometryof the reaction between the epoxy-amine resin and the diene functionalmono-isocyanate reactant and dieneophile-functionalized mono-isocyanatereactant used to make the diene-functionalizeddieneophile-functionalized epoxy-amine adduct.

In regard to coating compositions, the self-crosslinkable compositionsof the present invention are particularly adaptable for use in processesfor the cathodic electrodeposition of heat curable coatings, especiallyhighly alkali resistant primer coatings on automotive vehicle bodypanels. In such application the coatings provided by the invention arefound to be highly resistant to solvents and humidity and to provideexceptional corrosion protection for the underlying substrate. Theinvention is particularly advantageous in that the novel cure chemistryallows for low temperature curing of the coating. Suchself-crosslinkable composition of the invention adapted for cathodicelectrodeposition comprises substantially gel-free diene-functionalizeddieneophile-functionalized epoxy-amine adduct, at least partiallyneutralized with a solubilizing acid, typically an organic acid such as,for example, acetic acid or the like, which diene-functionalizeddieneophile-functionalized epoxy-amine adduct comprises the reactionproduct of:

(i) polyhydroxy functional epoxy-amine reactant of number averagemolecular weight about 300-10,000 comprising the reaction product ofpolyepoxide reactant having an average of at least about two epoxygroups per molecule with secondary amine reactant having a total of lessthan about 20 carbons per amino nitrogen, wherein each hydroxy group, ifany, of the secondary amine is removed at least 1 carbon from each aminonitrogen, such as, for example, diethanolamine; with

(ii) diene functional mono-isocyanate reactant; and with

(iii) dieneophile functional mono-isocyanate reactant;

which at least partially neutralized diene-functionalizeddieneophile-functionalized epoxy-amine adduct is dispersed in aqueoussolvent.

Such coating composition will deposit a heat curable coating at thecathode in an electrodeposition coating process according to techniqueswell known to the skilled in the art. Other features and advantages ofthe present invention will become more apparent from the followingdetailed description including the preferred embodiments and best modeof the invention.

DETAILED DESCRIPTION OF THE INVENTION

The self-crosslinkable epoxy-amine adduct of the invention is thereaction product of certain polyhydroxy functional epoxy-amine reactantwith diene functional mono-isocyanate reactant and dieneophilefunctional mono-isocyanate reactant. The polyhydroxy epoxy-amine can beformed in can be formed in non-aqueous medium by reacting any of certainsecondary amines with a di- or polyepoxide, that is, a polyepoxidehaving an average of at least about two epoxy groups per molecule. Thepolyepoxide is preferably free of carboxy ester moieties linking theepoxide groups, since such carboxy ester-free polyepoxides have beenfound to provide cured coatings according to the invention which aresignificantly more alkali resistant and provide significantly enhancedcorrosion protection to the underlying substrate.

One class of suitable polyepoxides includes reaction products of di- orpolyhydric, mono-, di- or polycyclic compounds with epihalohydrins ofthe formula ##STR1## wherein X is halogen such as chloro and Y ishydrogen or lower alkyl such as, for example, methyl or ethyl, whichepihalohydrin reaction products are exemplified by straight chain epoxyterminated compounds containing glycidyl ether groups such as bis-phenolA-epichlorohydrin reaction products. These are commercially availableas, for example, Epon 828, 1001 or 1004 (trademarks) marketed by ShellChemical Company, Houston, Texas, U.S.A. Such products contain aromaticgroups, such as benzene nuclei at a preferred average of at least aboutone, more preferably for this invention at least about two, for eachterminal epoxy group. Especially suitable are bis-phenol Aepichlorohydrin reaction products comprising in major amounts up to 10or more bis-phenol moieties within the epichlorohydrin reaction productbackbone, for example, those of number average molecular weight up toabout 8000, preferably 700-6000.

Other suitable polyepoxides include, for example, the Novolac epoxyresins, e.g. Epon 152 and 154 (trademarks) marketed by Shell ChemicalCompany, Houston, Texas, U.S.A. These polyepoxy resins includeepoxidized products of phenol formaldehyde resins that contain terminalglycidyl ether groups from aromatic moieties.

Aliphatic, including cycloaliphatic, epoxy compounds having, on theaverage, at least about two epoxy groups per molecule may also beemployed. Such aliphatic epoxy compounds include epihalohydrin andaliphatic di- or polyols such as glycol reaction products, epoxidizedpolybutadienes, vinylcyclohexenedioxide and dipentene dioxide. Stillfurther, hydrogenated bis-phenol A-epichlorohydrin products may also beemployed.

In one preferred embodiment, the polyepoxide comprises relatively highmolecular weight (e.g. number average above about 700) epoxy compoundhaving hydrophobic groups such as, for example, the reaction product ofepihalohydrin with diol, e.g. bis-phenol A. These have been found toadvantageously provide enhanced moisture resistance to the curedcoatings as compared to lower molecular weight epoxy compounds made inthis way. Alternatively, as will be more fully described hereinafter,certain lower molecular weight epoxy compounds may be reacted withsecondary alkanolamines to provide epoxy amine reaction products thatsimilarly provide enchanced moisture resistance. Preferably, however,the epoxy reactant comprises higher molecular weight epoxy compoundssuch as those bis-phenol A-epichlorohydrin reaction products having atleast about 25 mole percent, more preferably at least about 75 molepercent, constituent compounds that have two or more, preferably about3-10 aromatic groups per epoxy group.

Numerous additional suitable polyepoxide materials are commerciallyavailable or readily prepared using well known techniques andcommercially available starting materials, and these will be apparent tothe skilled of the art in view of the present disclosure. Compatiblemixtures of any of these epoxy compounds also are suitable.

The amine reactant preferably comprises secondary amine having a totalof up to about 20 carbons per amine nitrogen. More preferably at leastabout 75 mole percent of the amine reactant comprises at least one andpreferably two primary hydroxyl groups, each hydroxyl group on a carbonatom at least one carbon removed from any amino nitrogen. Preferredsecondary amine reactants include, for example, dialkylamine,dialkanolamine, N-alkylaniline and the like and a compatible mixture ofany of them, wherein each alkyl moiety and each alkanol moiety has fromone to about ten carbons, more preferably one to about six carbons. Mostpreferred are the lower dialkanolamines, especially diethanolamine, inview of their ready commercial availability, low cost, and ease ofreaction with the preferred polyepoxides. While not wishing to be boundby theory, it will be understood by the skilled in the art that theamine/epoxide reaction generates an hydroxyl group in the epoxy-amineadduct reaction product. Each such hydroxyl group of the epoxy-aminereaction product can react with the isocyanate functionality of a dienefunctional mono-isocyanate reactant or with the isocyanate functionalityof a dieneophile functional mono-isocyanate reactant. In addition, eachhydroxyl functionality contributed to the epoxy-amine adduct by analkanol moiety of the secondary amine will be available for reactionwith such isocyanate functionality. Accordingly, it will be understoodthat, as one significant advantage of the present invention, the degreeof diene and dieneophile functionalization of the degree of diene anddieneophile functionalization of the self-crosslinkable epoxy-amineadduct can be controlled to a large extent by selection of suitablesecondary amine or mixture of secondary amines. Thus, for example, theself-crosslinking epoxy-amine adduct will comprise more diene anddieneophile functionality, in toto, per molecule if dialkanol amine isemployed than if dialkylamine is employed. This assumes, of course, thatnear stoichiometric amounts of diene functional reactant and dieneophilefunctional reactant are employed in reaction with the polyhydroxyfunctional epoxy-amine reactant. In general, a greater degree of dieneand dieneophile functionalization will result in a cured coating havinga greater degree of crosslinking with corresponding physical properties.While it will be within the ability of those skilled in the art in viewof this disclosure to select secondary amines suitable to generate acomposition of the invention well adapted to a particular application,it has been found that diethanolamine provides generally superiorcoatings and, as mentioned above, is generally most preferred. If lessthan stoichiometric amounts of diene reactant and dieneophile reactantare employed and/or if mixed secondary amines are employed in reactionwith the polyhydroxy epoxy-amine reactant, then a mixed reaction productwill result which will, in general, function in a manner consistent withthe foregoing description.

According to one embodiment of the invention, combinations of primaryand secondary amines can be employed with lower molecular weightpolyepoxides to increase the molecular weight of the epoxy-aminereaction product. However, secondary mono-amines are preferred, withdiethanolamine being most preferred.

A class of preferred hydroxy functional amine reactants includes thoseof general formula: ##STR2## wherein R and R' are independently straightor branched chain monovalent aliphatic moieties of up to about 10carbons each, providing that at least one and preferably both R and R'are substituted by hydroxy on a primary carbon atom that is not adjacentto any amino nitrogen. R and R' can also form part of a ring compound,such as a six member ring. More preferably, R and R' are independentlyalkyl and desirably up to 7 carbons each, even more desirably up to 4carbons each.

The polyepoxide and amine reactants are reacted at conditions that allowopening of the epoxy ring by amino nitrogen and provide a gel-freereaction product. The reaction of the epoxy functionality with secondaryamine can be expected to yield tertiary amino groups, whereas reactionwith primary amines can be expected to yield secondary amino groupswhich may undergo further reaction with an unreacted epoxy functionalityof the same or more probably of another polyepoxide molecule, resultingin chain extension.

Suitable reaction conditions and techniques are well known to theskilled of the art and will be apparent from the present disclosure.Thus, for example, the reaction medium preferably comprises non-aqueousmedium that may be of diverse but preferably polar character and servesto maintain contact of reactants, control reaction speed, maintaindesirable viscosity and other functions well known in the art. Thus,suitable solvents and diluents for the reaction medium include aromaticand aliphatic hydrocarbons, halides, ethers, ketones such as methylamylketone, n-amyl ether, xylene, oxygenated solvents such as cellosolves,for example, butyl Cellosolve acetate, hexyl Cellosolve acetate and thelike, carbitols, for example carbitol acetate, and the like includingmixtures of these.

Elevated reaction temperatures may be employed to facilitate reactionbetween the polyepoxide reactant and the amine reactant and the reactionmay be conducted stepwise. The reactants are used preferably instoichiometric amounts. That is, it is preferred that sufficientsecondary amine reactant be used to react substantially all epoxyfunctionality of the polyepoxide reactant. More specifically, forexample, about 0.9-1.0 equivalent secondary amine functionality isreacted with about 1 to 1.1 equivalent epoxide functionality to yieldpolyhydroxy epoxy-amine adduct which is substantially free of unreactedepoxy functionality. More specifically, the polyhydroxy epoxy-amineadduct reaction product should contain less than 20% of the originalunreacted epoxy groups, more desirably less than about 10% and mostpreferably less than about 5% unreacted epoxy groups, based on thenumber originally present.

The above described polyhydroxy epoxy-amine reactant isdiene-functionalized by reacting same with diene functionalmono-isocyanate reactant. Suitable diene functional mono-isocyanates arereadily prepared employing readily available reactants according tomethods apparent to the skilled of the art in view of the presentdisclosure. In general, mono-diene functional mono-isocyanate reactantsare preferred in view of their ease of preparation, and most preferredare those of formula O═C═N--R--A, wherein R is a bivalent hydrocarbonlinking moiety which is substantially unreactive with isocyanatefunctionality and with substituent A, and A is a monovalent olefinicmoiety having 1,3-conjugated double bonds according to formula I:##STR3## wherein: ##STR4## or the like, wherein R¹ is hydrogen,straight, branched or cyclo alkyl, aryl, arylalkyl or the like, and eachR² is the same or different and each is hydrogen, hydroxy, carboxy,straight, branched or cyclo alkyl, aryl arylalkyl, or the like, eachalkyl, aryl and arylalkyl moiety of R¹ and R² being unsubstituted ormono- or poly-hydroxy substituted or mono- or poly-amino substituted;and

X¹, X², X³, X⁴ and X⁵ are the same or different and each is hydrogen,hydroxy, carboxy, amino, straight, branched or cyclo alkyl, aryl,arylakyl, cyano, nitro, or the like, or X¹ and X⁵ together are alkylene,--O--, --NR¹ --, wherein R¹ is as defined above, or like divalent group(resulting in a cyclic diene moiety), each alkyl, aryl, arylalkyl andalkylene moiety of X¹, X²,X³, X⁴ and X⁵ being unsubstituted or mono-, orpoly-hydroxy substituted or mono- or poly-carboxy substituted or mono-or poly-amino substituted. According to one most preferred embodiment,diene moiety A is: ##STR5##

One group of preferred diene functional mono-isocyanate reactantsinclude the reaction products of one molar equivalent of suitablediisocyanate with one molar equivalent of diene reactant selectedpreferably from the group consisting of monohydroxy functional dienereactants, monoamino functional diene reactants and like mono- andpoly-diene functional reactants have a single functionalitysubstantially reactive with the diisocyanate reactant, or a compatiblemixture of any such diene functional reactants. Exemplary preferreddiene functional reactants include those of molecular weight about30-500 such as furfuryl alcohol, furfuryl amine,2-hydroxymethyl-1,3-butadiene, 2-aminomethyl-1,3-butadiene and the like.Also suitable are polydiene-functional reactants, of which many arereadily prepared employing commercially available reactants according tomethods apparent to the skilled of the art in view of the presentdisclosure. A polydiene functional reactant may be preferred where therate of reaction is relatively slow between the particular diene anddieneophile functionality of the crosslinkable composition, to improvethe cure response of the composition.

Suitable organic diisocyanate reactants are readily commerciallyavailable and include many known to the skilled of the art such as, forexample, phenylene diisocyanates, toluene diisocyanate, isophoronediisocyanates, diisocyanatoalkane wherein the alkylene moiety has,preferably, from about three to about ten carbons, for example,1,6-hexane diisocyanate, or the like or a compatible mixture of any ofthem. Most preferably the organic diisocyanate has a molecular weightless than about 250. If corrosion resistance is of primary concern inthe cured coating, for example in the case of an automotive vehicleprimer or topcoat, it may be preferred to use an aliphatic diisocyanate,for example, isophorone diisocyanate and 1,6-hexane diisocyanate.Aromatic diisocyanates provide suitable coatings, however, and may bepreferred in view of their lower cost.

The diene reactant and the diisocyanate reactant can be reactedaccording to well known techniques. Accordingly, approximately one molarequivalent of diene reactant can be added to a suitable amount ofdiisocyanate under reaction conditions. Well known techniques can beemployed to maximize the yield of the diene functional mono-isocyanatereaction product, such as, for example, adding the diene reactant slowlyto an excess of the organic diisocyanate under reaction conditions.

The polyhydroxy epoxy-amine reactant is dieneophile functionalized byreacting same with a dieneophile functional mono-isocyanate. Suitabledieneophile functional mono-isocyanates are readily prepared employingreadily available reactants according to methods apparent to the skilledof the art in view of the present disclosure. In general,mono-dieneophile functional mono-isocyanate reactants are preferred inview of their ease of preparation and most preferred are those offormula O═C═N-R'-B, wherein R' is a bivalent hydrocarbon linking moietywhich is substantially unreactive with isocyanate functionality and withsubstituent B, and B is a dieneophile moiety reactive at elevated curetemperature with the aforesaid diene moiety A. The dieneophile moiety Bis preferably of molecular weight about 30-200. Preferred dieneophilemoieties include those according to formula II-A to II-H: ##STR6## orthe like, wherein X⁰, X¹, and each X² are the same or different aspreviously defined for formula I; X⁶ is ##STR7## unsubstituted, or mono-or poly-hydroxy substituted or mono- or poly-carboxy substituted ormono- or poly-amino substituted alkanyl-ylidene of 2 or 3 carbons; eachX⁷ is the same or different and each is a covalent bond, ##STR8## or thelike; X⁸ is hydrogen, hydroxy, carboxy, amino, straight or branched orcyclo-alkyl, aryl, arylalkyl, cyano, nitro or the like, each alkyl, aryland arylalkyl moiety of X⁸ being unsubstituted, mono- or poly-hydroxysubstituted or mono- or poly-carboxy substituted or mono- or poly-aminosubstituted; or X¹ and X⁸ together are --(CX²)_(n) -- wherein n is aninteger from about 3 to about 7, preferably about 3 to 4. According toone most preferred embodiment, dieneophile moiety B is: ##STR9##

One group of preferred dieneophile functional mono-isocyanate reactantsincludes the reaction products of one molar equivalent of suitablediisocyanate with one molar equivalent of dieneophile reactant selectedpreferably from the group consisting of monohydroxy functionaldieneophile reactants, monoamino functional dieneophile reactants andlike mono- and poly-dieneophile functional reactants having a singlefunctionality substantially reactive with the diisocyanate reactant, ora compatible mixture of any of them. Exemplary preferred dieneophilefunctional reactants include those of molecular weight about 50-500 suchas monohydroxy or monoamino or like isocyanate-reactive ene reactants,for example, methylolmaleimide, hydroxypropyl-methacrylate, allylalcohol, allyl amine, hydroxyethyl-methacrylate, hydroxyethylacrylateand the like and a compatible mixture of any of them. Also suitable forreaction are poly-dieneophile functional reactants, of which many arereadily prepared employing commercially available reactants according tomethods apparent to the skilled of the art in view of the presentdisclosure. A polydieneophile reactant may be preferred, for example,where the rate of reaction is relatively slow between the particulardiene and dieneophile functionality of the crosslinkable composition, toimprove the cure response of the composition.

Suitable and preferred diisocyanates are those disclosed above inconnection with the synthesis of diene functional mono-isocyanate. Thedieneophile reactant and the diisocyanate reactant can be reactedaccording to well known techniques. Accordingly, approximately one molarequivalent of the dieneophile reactant can be added to the diisocyanateunder reaction conditions. Well known techniques can be employed tomaximize the yield of the dieneophile functional mono-isocyanatereaction product, such as, for example, adding the dieneophile reactantslowly to an excess of the organic diisocyanate under reactionconditions.

The self-crosslinkable epoxy-amine addjust of the invention is thereaction product of the above described hydroxy functional epoxy-aminereactant with the dienefunctionalized mono-isocyanate and with thedieneophilefunctionalized mono-isocyanate. The reactions can be carriedout either simultaneously or sequentially. The reactants preferably areused in approximately stoichiometric amount. That is, it is preferredthat a sufficient amount is used of diene functional mono-isocyanatereactant and dieneophile functional mono-isocyanate reactant, in toto,to react substantially all hydroxy functionality of the polyhydroxyepoxy-amine reactant. Each diene moiety and dieneophile moiety of theself-crosslinkable epoxy-amine adduct will be available for crosslinkingand chain-extension reaction with a dieneophile moiety and diene moiety,respectively, of another such epoxy-amine adduct during heat curing ofthe composition.

To obtain the self-crosslinkable epoxy-amine adduct in substantiallygel-free state, it will be apparent to the skilled of the art in view ofthe present disclosure, that the diene and dieneophile functionalityshould be selected such that the rate of reaction of the dienefunctionality with the dieneophile functionality will be substantiallyless, preferably far less, than that of the hydroxy functionality withthe isocyanate functionality under the reaction conditions employed toreact the polyhydroxy epoxy-amine reactant with the diene functionalmono-isocyanate and dieneophile functional mono-isoycanate. The reactionproduct, that is, the self-crosslinkable epoxy-amine adduct, preferablyprovides number average diene and dieneophile functionality, in toto, ofat least about three, to provide good crosslink density in the curedcomposition. More preferably the self-crosslinkable epoxy-amine adductprovides number average diene and dieneophile functionality, in toto, ofabout 3-20 per molecule. Further, the diene functional mono-isocyanatereactant and the dieneophile functional mono-isocyanate reactantpreferably are used in approximately stoichiometric amount. That is, itis preferred that one diene molar equivalent of the former be used withapproximately one dieneophile molar equivalent of the later. In general,the diene and dieneophile reactants can be used in molar equivalentratio of about 1:8 to about 1.1.2, respectively.

According to an alternative embodiment of the invention, substantiallyless than all hydroxy functionality of the polyhydroxy epoxy-aminereactant are reacted. The resulting self-crosslinking epoxy-amine adductwould comprise a mixed reaction product and would introduce hydroxyfunctionality into the self-crosslinkable compositoin of the invention.In this embodiment, the self-crosslinkable composition of the inventioncan further comprises suitable crosslinking agent reactive with suchhydroxy functionality. Numerous such crosslinking agents are well knownto the skilled of the art and include, for example, any of a variety ofaminoplast crosslinking agents, for example, partially alkylatedmelamines (melamines formaldehyde resins modified by alcohols), forexample, partially methylated melamines and butylated melamines,polyalkyl ethers of the polymethylol melamines, for example, hexamethoxymethylmelamine; urea formaldehyde condensate modified by alcohol, forexample, paraformaldehyde and trioxane; polymethylol compounds ofhexamethylene diurea; adipic acid dimethylol amide and methylol etherthereof; tetramethylolhydrazodicarbonamide; polymethylol compounds ofpolycaprolactum and methylol ethers thereof; and the like and compatiblemixtures of any of them. Other suitable crosslinking agents will beapparent to the skilled of the art in view of the present disclosure.Butylated melamines are preferred since they are readily commerciallyavailable and provide suitable crosslinking activity with theepoxy-amine adduct of the invention. The crosslinking agent can be usedup to stoichiometric amount, that is, up to amount sufficient to reactsubstantially all such hydroxy functionality. If an aminoplastcrosslinking agent is employed, then it may be advantageous in certainembodiments or for certain applications to include in the compositionany of a variety of compatible catalysts known to the skilled of the artto catalyze the crosslinking reaction, for example, paratoluenesulfonicacid, phosphoric acid, phenol acid phosphate, butyl maleate and the likeor a compatible mixture of any of them. In addition, a flow controlagent, for example, polybutylacrylate; a wetting agent, for example,silicone; pigments; a pigment dispersent; and/or a corrosion inhibitor,for example, chromate pigment, several of all of which are known to theskilled of the art, may be employed in the coating compositions of theinvention.

Di- and polyhydroxy compounds of diverse character may be employed alsoin the composition of the invention to modify the properties of thecomposition (i.e. the properties prior to or following cure) as well asto act as solvent, including reactive solvent, for solubilizing theself-crosslinkable epoxy-amine adduct. Thus, for example, thesecompounds may impart increased flexibility or reduce cratering inspray-applied cured films comprising the self-crosslinkable epoxy-amineadduct of the invention. A preferred class of hydroxy compounds includesaliphatic dihydroxy compounds, especially glycols and glycol ethers ofthe formula HO(C_(a) H_(2a) O)_(x) -(C_(b) H_(2b) O)_(y) H wherein a, b,x and y are independent integers and a and b are from 2 to 6 and x and yare from 0-10 with the sum of x and y being 10. Examples includeethylene glycol, dipropylene glycol, and 1,6-hexanediol. Another classof glycols includes hydroxy terminated polybutadienes, hydrogenatedbis-phenol-A, such hydroxy compounds being of generally hydrophobiccharacter and molecular weights of about preferably 100-5000, numberaverage. Higher boiling solvents (e.g. boiling point above about 180° C.as 190°-250°) that are of polar character may tend to interact with theresinous components of crosslinking composition and thereby allow highersolids content. If such hydroxy functional compounds are included in thecomposition of the invention, then crosslinking agent reactive withhydroxy functionality, such as described above, should be employed,preferably in stoichiometric amount.

As noted above, pigments may be used in the primer compositions of theinvention in accordance with known techniques. Pigments are employedmost typically, for example, to enhance the efficacy of compositionsemployed as coating compositions over corrosion-susceptible substrates.Chromate pigments, in particular, have been used to enhance corrosionprotection. It is, however, a significant advantage of the presentinvention that chromate pigments need not be employed in compositionsemployed as such coating compositions over corrosion susceptiblesubstrates. Cured coating of the invention are highly alkali resistantand provide excellent corrosion protection even without chromatepigments. Such pigments and others can be employed, however, and may bedesirable for aesthetic purposes. Exemplary pigments include titaniumdioxide, silica, carbon black, and barytes and are employed typically atpigment : binder weight ratios of about 40:60 to about 60:40.

While not wishing to be bound by theory, it is presently understood thatduring the curing process at elevated temperature, the dienefunctionality and the dieneophile functionality react with each otherthrough Diels Adler cycloaddition chemistry. Taking the dieneophilefunctionality to be ene functionality for purposes of illustration, itis presently understood that the ene/diene reaction results in theformation of a cyclic six membered ring: ##STR10## In like manner, thecycloaddition reaction of a cyclic diene with an ene moiety yields abicyclic carbon-carbon linkage: ##STR11## Such Diels Alder reactionshave been studied and several parameters have been identified whichaffect reactivity. Exemplary such work is found in P. Wasserman, "DielsAlder Reactions", Elsevier Publishing Co., New York, 1965, which isincorporated herein by reference. Such parameters are found to includemost notably the selection of the substituent groups on the diene anddieneophile moieties, steric hindrance at the reaction site andmolecular orientation. In this regard, it is one characterizing aspectof the present invention that the substituent groups on the dienefunctionality and on the dieneophile functionality employed in theresins of the invention are selected to provide the desired degree ofreactivity, that is, cure response. In particular, the degree ofreactivity is increased by ene moiety substitution groups which, in neteffect, are electron withdrawing, that is, which increase the electronaffinity of the ene functionality double bond. Thus, for example,reactivity is increased by electron withdrawing ene substitution groupssuch as nitro, cyano, ester ##STR12## nitrile, carbonyl, straight,branched or cyclo alkyl or alkylene, arylene, aralkylene, --O--, --NR--,--S-- and the like. Similarly, it will be understood by the skilled ofthe art in view of the present disclosure, that the shelf stability ofthe resins is enhanced by ene moiety substitution groups which, in neteffort, are electron donating, that is, which decrease the electronaffinity of the ene functionality double bond. Thus, shelf life isincreased by substituent groups such as, for example, amine and etherlinkages, sulfoxide, sulfone, urethane and the like.

It will be within the ability of those skilled in the art, in view ofthe present disclosure, to select dieneophile substituent groups whichprovide, in net effect, the desired compromise between shelf stabilityand reactivity. It generally is preferred that no electron donatinggroup(s) be substituted directly on either carbon of the enefunctionality double bond, nor on any adjacent or next adjacent atom. Incertain applications, however, particularly where extended shelf life isof paramount importance, such electron donating groups can be tolerated,more preferably in conjunction with electron withdrawing group(s) ofgreater effect, and with sufficient reaction catalyst, higher curetemperatures, longer cure periods, or a combination thereof.

In view of the present disclosure, it will be appreciated by the skilledof the art that in accordance with the foregoing discussion, theself-crosslinkable epoxy-amine adduct of the invention are rendered morereactive by diene-functionality wherein the diene moiety substitutiongroups are electron donating in net effect, that is, wherein theelectron affinity of the diene double bonds is increased. Likewise,electron withdrawing groups on the diene moiety increase the shelfstability of the composition. It generally is preferred that no electronwithdrawing group(s) be substituted directly on any carbon of eitherdiene functionality double bond, nor on any adjacent or next adjacentatom. As noted above, however, in certain applications an epoxy-amineadduct of the invention may require extended shelf life or for someother reason call for or tolerate diene-functionality comprisingelectron withdrawing substitution groups on the diene moiety.

Applications

As noted above, the self-crosslinkable epoxy-amine adduct of theinvention is useful in a variety of applications including, especially,as a coating composition to provide an aesthetic and/or protective filmon a substrate. In particular, the self-crosslinkable epoxy-amine adductof the invention can be formulated into a variety of primer formulationsincluding both aqueous primer formulations and non-aqueous primerformulations. Such primers can be used as coatings for bare or treatedsteels (e.g., conversion coated with phosphates) as well as for guidecoats over previously deposited primers applied, for example, byelectrodeposition. Conventional modifying ingredients can be used insuch primer formulations including, for example, flow control agents,pigments, pigment dispersents, thixotropes, anti-cratering aids, photostabilizers and the like, as indicated above.

Solvent Based Primers

Coating compositions comprising diene-functionalizeddieneophile-functionalized epoxy-amine adduct can be dispersed inorganic solvent and applied to a substrate, for example a ferrous metalsubstrate, according to well known techniques such as by spray, curtain,dip and other coating methods. For solvent-based coatings to be appliedby spray application methods, the self-crosslinkable epoxy-amine adductis preferably of number average molecular weight about 500-5000, morepreferably about 800-2000. It will be within the ability of thoseskilled in the art to determine a suitable solvent and amount of samefor a given coating composition of the invention, for a givenapplication. It will be understood that any solvent allowed to remain inthe cured coating should be inert so as to avoid adverse effects uponthe cured coating or upon another coating used in conjunction with it,during the curing process or thereafter. Preferably the cured coating issubstantially free of solvent. Sufficient solvent is used to reduce theviscosity of the coating composition to a level suitable for applicationto the substrate in the desired manner. Thus, for example, for acomposition to be used as a spray-applied primer coating composition, itis preferred that sufficient solvent be used to reduce the viscosity ofthe coating composition to about 25-35 seconds, No. 4 Ford Cup at 27° C.(80° F.).

Solvent based coating compositions according to the invention are curedby heating same to a sufficient temperature for a sufficient time todrive off the solvent and to cause reaction of the diene functionalitywith the dieneophile functionality and of the hydroxyl functionality, ifany, with the crosslinking agent, if any. Thus, for example, a solventbased coating composition comprising the self-crosslinkable epoxy-amineadduct of the invention according to preferred embodiments describedabove, applied by spray techniques to the surface of an automotivevehicle body panel as a primer coat would be cured by heating to atemperature of about 130°-210° C. for approximately 15-30 minutes.

Water Based Coating Compositions

The self-crosslinkable epoxy-amine adduct of the present invention canbe formulated into water based coating compositions. Accordingly, thediene-functionalized dieneophile-functionalized epoxy-amine adduct is atleast partially neutralized by acid, preferably weak organic acid suchas formic, acetic acid which is generally preferred, latic, butryric orthe like or a compatible mixture of any of them. Additional suitableneutralizing acids (often referred to as "solubilizing acid") are knownto the skilled of the art and will be apparent in view of the presentdisclosure. The at least partially neutralized epoxy-amine adduct isdispersed into water, preferably de-ionized water for use either inspray application methods, flow coating, etc. or electrodepositionmethods. Cured coatings resulting from such methods are found to provideexceptionally good flow characteristics resulting in smooth andotherwise aesthetically superior films having exceptionally good solventand humidity resistance. The cured coatings were also found to be highlyalkali resistant and thus, to provide exceptionally good corrosionprotection to the underlying substrate. Water based coating compositionsaccording to the invention can be employed in spray applicationtechniques. Thus, for example, they can be employed as a spray-appliedprimer coat for automotive vehicle body panels.

Coating compositions of the invention wherein the self-crosslinkableepoxy-amine adduct is applied to the surface of a substrate byelectrodeposition technique is a particularly preferred embodiment ofthe invention. According to this embodiment, the self-crosslinkableepoxy-amine adduct is at least partially, and preferably substantiallytotally neutralized with solubilizing acid and thereafter dispersed intode-ionized water to a concentration of about 5-25 weight percent, morepreferably about 10-15 weight percent. The resulting water basedcomposition is adapted for use as a cathodic electrocoat composition.That is, the coating comprising the self-crosslinkable epoxy-amineadduct and crosslinking agent, catalysts, etc., if any, will depositupon the workpiece acting as the cathode according to knownelectrodeposition systems and techniques. For coating compositionsadapted for cathodic electrodeposition, the self-crosslinkableepoxy-amine adduct is preferably of number average molecular weightabout 800-10,000, more preferably about 2000-8000.

Cathodic electrodeposition according to the present invention is donepreferably at voltages of about 1-500 volts, more preferably about200-400 volts. Subsequent to electrodeposition, the coating on thesubstrate is heated to above about 130° C., more preferably about150°-210° C. for a time sufficient to effect the diene/dieneophilereaction and to drive off substantially the entire aqueous solventcontent of the coating. Employing a self-crosslinkable epoxy-amineadduct according to preferred embodiments described above, the coatingwill be substantially completely cured following baking at about 158° C.for about 30 minutes. In general, it will be within the ability of thoseskilled in the art to select suitable electrodeposition voltage andbaking temperatures and like process parameters in view of theparticular application involved.

Such aqueous solvent based coating compositions can comprise a mixtureof water and water compatible solvent ("coupling solvents") and diluentssuch as ethylene glycols and alkylated glycols, for example oxygenatedsolvents such as Cellosolves and carbitols and the like or a compatiblemixture of any of them. In this case, the self-crosslinkable epoxy-amineadduct preferably is initially prepared in suitable "coupling solvent".Any attempt to replace other solvents such as methyl ethyl ketone withcoupling solvents by known distillation techniques could cause the resinto self-crosslink. It will be well within the skill of the art toprepare the self-crosslinkable epoxy-amine adduct according to themanner described above, employing suitable coupling solvent, for examplebutyl Cellosolve acetate. For use as spray primers, for example, suchwater based coating compositions can be formulated with high levels ofwater, for example, greater than about 10%, such as about 30-50% byweight, and yet cure within conventional conditions such as, forexample, at temperatures above about 130° C., more preferably about150°-210° C., in about 30 minutes, or even less according to preferredembodiments. Obviously, the particular time and temperatures necessaryto effect curing of the coating will depend upon the particularepoxy-amine adducts employed in the coating composition and will dependupon the thickness of the coating, the use of catalysts, and likeparameters familiar to the skilled of the art.

The invention will be further understood by referring to the followingdetailed examples. It should be understood that these examples arepresented by way of illustration and not by way limitation. Unlessotherwise specified, all references to "parts" are intended to meanparts by weight.

EXAMPLE I

This example illustrates the preparation of a polyhydroxy epoxy-aminereactant from higher molecular weight Bisphenol A-epichlorohydrin epoxyresin and dialkanolamine. To a solution of 93 g (0.1 molar equivalentweight) of Epon 1004¹ (trademark) in 93 g butoxy ethyl acetate was added10.5 (0.1 mole) diethanol amine. The reaction mixture was heated to70°-80° C. and maintained at that temperature for four hours. Thepolyhydroxy epoxy-amine reaction product, shown to be epoxide free uponIR analysis by absence of 910 cm⁻¹ peak, was cooled to room temperatureand stored.

EXAMPLE II

This example illustrates the preparation of a polyhydroxy epoxy-aminereactant from higher molecular weight Bisphenol A-epichlorohydrin epoxyresin and monoalkanolamine. Following the procedures of Example I 7.4 g(0.1 mole) of N-methyl ethanol amine is reacted with 93 g of Epon 1004¹(trademark) in 93 g butoxy ethyl acetate. The epoxide free polyhydroxyepoxy-amine reaction product is cooled to room temperature and stored.

EXAMPLE III

This example illustrates the preparation of a polyhydroxy epoxy-aminereactant from a lower molecular weight Bisphenol A-epichlorohydrin epoxyresin and dialkanolamine. Following the procedures of Example I, 10.5 g(0.1 mole) diethanol amine is reacted with 19.0 g (0.1 molar equivalentweight) Epon 828² (trademark) in 93 g butoxy ethyl acetate. The epoxidefree polyhydroxy epoxy-amine reaction product is cooled to roomtemperature and stored.

EXAMPLE IV

This example illustrates the preparation of polyhydroxy epoxy-aminereactant from low molecular weight aliphatic diepoxide anddialkanolamine. Following the procedures of Example I, 10.5 g (0.1 mole)diethanol amine is reacted with 20.2 g (0.1 molar equivalent weight)1,4-butane diol diglycidyl ether. The epoxide free polyhydroxyepoxy-amine reaction product is cooled to room temperature and stored.

EXAMPLE V

This example illustrates the preparation of an ester-bearing polyhydroxycyclic aliphatic epoxy-amine reactant. Following the procedures ofExample I, 126 g (0.1 mole) Araldite Cy 179³ (trademark) is reacted with10.5 g dialkanolamine in 130 g butanol. The epoxide free polyhydroxyepoxy-amine reaction product is cooled to room temperature and stored.

EXAMPLE VI

This example illustrates the preparation of dieneophile functionalmono-isocyanate reactant having a relatively less reactive dieneophilemoiety. To a solution comprising 222 g (1.0 mole) isophoronediisocyanate and 1 g dibutyl tin dilaurate in 100 g methyl ethyl ketoneheated to 60°-80° C. was added a solution of 70 g (1.0 mole) allylalcohol in 73 g methyl ethyl ketone. The reaction mixture was maintainedat 60°-80° C. for one hour following the addition. The dieneophilefunctional mono-isocyanate reaction product was cooled to roomtemperature and stored.

EXAMPLE VII

This example illustrates the preparation of a dieneophile functionalmono-isocyanate reactant having a moderately reactive dieneophilemoiety.

Step A: preparation of maleate. To a solution of 19.6 g (0.2 mole)maleic anhydride in 13.1 g methyl ethyl ketone was added 6.4 g methanoland 100 mg. triethylamine. The reaction was heated to 60°-80° C. andmaintained at that temperature for about one hour and then usedimmediately in Step B.

Step B: preparation of substituted maleate having the structure:##STR13## To the entire reaction mixture of Step A, at about 60° C., wasadded 26 g (0.2 mole) butyl glycidyl ether and 0.15 g Cordova AMC-2⁴(trademark) catalyst. The reaction mixture was again heated for aboutsix hours until all epoxide functionality had reacted as shown by IRanalysis.

Step C: preparation of diene functional mono-isocyanate. The procedureof Example VI was followed using the entire contents of the reactionmixture of Step B with 44 g (0.2 mole) isophorone diisocyanate anddibutyl tin dilaurate as catalyst. The dieneophile functionalmono-isocyanate reaction product was cooled to room temperature andstored.

EXAMPLE VIII

This example illustrates the preparation of dieneophile functionalmono-isocyanate having relatively highly reactive dieneophile moiety.Following the procedures of Example VI, 127 g (1.0 mole)methylolmaleimide was reacted with 222 g (1.0 mole) isophoronediisocyanate. The dieneophile functional mono-isocyanate was cooled toroom temperature and stored.

EXAMPLE IX

This example illustrates the preparation of cyclic diene functionalmono-isocyanate. To a solution of 222. g (1.0 mole) isophoronediisocyanate and 1 g dibutyl tin dilaurate in 100 g methyl ethyl ketonewas added a solution of 98 g (1.0 mole) furfuryl alcohol in 100 g methylethyl ketone. The rate of addition was controlled to maintain reactiontemperature of 60°-80° C. Following addition of the furfuryl alcohol,the reaction mixture was maintained at 60°-80° C. by external heatingfor an additional hour. The cyclic diene functional mono-isocyanatereaction product was cooled to room temperature and stored at roomtemperature.

EXAMPLE X

This example illustrates the preparation of acyclic diene functionalmono-isocyanate. Following the procedure of Example IX, 84 g (1.0 mole)2-hydroxymethyl-1,3-butadiene is reacted with 222 g (1.0 mole)isophorone diisocyanate. The reaction temperature, however, ismaintained at 30°-45° C. The acyclic diene functional mono-isocyanatereaction product is cooled and stored at room temperature.

EXAMPLE XI

This example illustrates the preparation of a relatively shelf-stableself-crosslinkable epoxy-amine adduct according to the presentinvention. A four step procedure is followed. First, polyhydroxyepoxy-amine reactant is prepared according to the procedure of ExampleI, employing 9.37 g (0.01 molar equivalent) of Epon 1004¹ (trademark)with 1.05 g (0.01 mole) of diethanol amine in 10 g butoxy ethyl acetate.Second, diene functional mono-isocyanate is prepared according to theprocedure of Example IX, employing 8.88 g of isophorone diisocyanatewith 3.92 g furfuryl alcohol and 0.1 g dibutyl tin dilurate in 10 gbutoxy ethyl acetate. Third, dieneophile functional mono-isocyanate isprepared according to the procedure of Example VI, employing 1.16 g(0.01 mole) of hydroxy ethyl acrylate with 2.22 g (0.01 mole) ofisophorone diisocyanate in 3.3 g methyl ethyl ketone with 10 mg ofdibutyl tin dilurate. Finally, the self-crosslinkable epoxy-amine adductof the invention is prepared by combining the polyhydroxy epoxy-aminereactant with the diene functional mono-isocyanate and the dieneophilefunctional mono-isocyanate at room temperature. The reaction mixture isstirred constantly until all isocyanate functionality is reacted, asdetermined by IR analysis. The resulting self-crosslinkablepolydiene-functionalized polydieneophile-functionalized epoxy-amineadduct is suitable for use in self-crosslinkable compositions of thepresent invention.

EXAMPLE XII

A highly reactive self-crosslinkable epoxy-amine adduct according to thepresent invention was prepared according to the method of Example XI,employing 1.27 g (0.01 mole) of methylol maleimide in lieu of thehydroxy ethyl acrylate. The resulting self-crosslinkablepolydiene-functionalized polydieneophile-functionalized epoxy-amineadduct is found to gel within 60-120 minutes at room temperature.

EXAMPLE XIII

This example illustrates a typical pigment package suitable for use in acoating composition according to the present invention.

PIGMENT PACKAGE

Aluminum silicate: 7.0 g

White lead: 5.6 g

Carbon Black: 1.0 g

EXAMPLE XIV

This example illustrates the preparation of a solvent-based primercoating composition according to the present invention. One half of theentire epoxy-amine adduct product of Example XI is combined with thepigment package of Example XIII and the resulting mill base is grounduntil a Hegman Gauge reading of at least 7 is obtained. The remainingportion of the epoxy-amine adduct of Example XI is added and thecomposition is thoroughly mixed, its viscosity is reduced with methylethyl ketone to 30-40 sec., No. 4 Ford Cup (27° C.), and it is filtered.The resulting solvent-based composition is suitable for use by sprayapplication methods as a primer coat for corrosion protection of anunderlying substrate.

EXAMPLE XV

This example illustrates the use of a crosslinkable composition ofmatter according to the present invention. The solvent-based primercomposition of Example XIV is applied by spray technique to bare,unpolished steel panels and cured by baking at 180° C. for 30 minutes.The cured coating provides good resistance to corrosion of the steelsubstrate.

EXAMPLE XVI

This example illustrates the preparation of an aqueous solvent-basedcathodic electrodepositable coating composition according to the presentinvention. The self-crosslinkable epoxy-amine adduct is preparedaccording to the procedure of Example XI, except that a couplingsolvent, butyl Cellosolve acetate, is used to facilitate subsequentdispersion of the resin into aqueous medium suitable forelectrodeposition. One half of the resulting epoxy-amine adduct iscombined with the pigment package of Example XIII and the resulting millbase is ground until a Hegman Gauge reading of at least 7 is obtained.The remaining portion of the epoxy-amine adduct is added and mixedthoroughly. The mixture is partially neutralized with 6.0 g glacialacetic acid and is dispersed slowly into 150.0 g of deionized water. Theresulting aqueous formulation is filtered. The aqueous solvent-basedcomposition is suitable for use in cathodic electrodeposition coatingoperations to deposit a primer coat for corrosion protection of asuitable substrate.

EXAMPLE XVII

This example illustrates the use of a crosslinkable composition ofmatter according to the present invention. The aqueous solvent-basedcomposition of Example XVI is applied by cathodic electrodepositionmethods, at 100-300 volts, to bare, unpolished steel panels. Thecomposition is cured by baking the coated panels at 180° C. for 30minutes. The cured coating is found to provide good resistance tocorrosion of the underlying substrate.

In view of this disclosure, many modifications of this invention will beapparent to those skilled in the art. It is intended that all suchapparent modifications fall within the true scope of this invention andbe included within the terms of the appended claims.

INDUSTRIAL APPLICABILITY

It will be apparent from the foregoing that this invention hasindustrial applicability as a coating composition, especially as acathodic electrodeposition primer coating composition for sheet steeland the like used in automotive vehicles, household appliances and thelike, and other applications where the coating composition desirably hasexcellent storage stability and the cured coating desirably providesexcellent humidity and solvent resistance to protect the substrateagainst corrosion, wear and the like.

What is claimed is:
 1. A self-crosslinkable substantially gel-freeconjugated diene-functionalized dieneophile-functionalized epoxy-amineadduct, preferably of number average molecular weight about 500-8000,comprising the reaction product of (i) polyhydroxy functionalepoxy-amine reactant comprising the reaction product of polyepoxyreactant having an average of at least about 2 epoxy groups per moleculewith secondary amine reactant having a total of less than about 20carbons per amino nitrogen, wherein each hydroxy group, if any, of thesecondary amine is removed at least 1 carbon from each amino nitrogen,with (ii) conjugated diene functional mono-isocyanate reactant and with(iii) dieneophile functional mono-isocyanate reactant other than saidconjugated diene functional mono-isocyanate reactant.
 2. Theself-crosslinkable epoxy-amine adduct of claim 1, wherein the polyepoxyreactant for said polyhydroxy functional epoxy-amine reactant isselected from the group consisting of Bisphenol A-epichlorohydrin epoxyresin, Novolak epoxy resin, aliphatic epoxy resins and a compatiblemixture of any of them.
 3. The self-crosslinkable epoxy-amine adduct ofclaim 1, wherein the polyepoxy reactant for said polyhydroxy functionalepoxy-amine reactant has number average molecular weight about 700-8000.4. The self-crosslinkable epoxy-amine adduct of claim 1, wherein saidsecondary amine reactant said polyhydroxy functional epoxy-aminereactant is selected from the group consisting of dialkylamine,dialkanolamine, N-alkylaniline and a compatible mixture of any of them,wherein each alkyl moiety and each alkanol moiety has from one to aboutten carbons.
 5. The self-crosslinkable epoxy-amine adduct of claim 3,wherein said secondary amine reactant for said polyhydroxy functionalepoxy-amine reactant consists essentially of diethanolamine.
 6. Theself-crosslinkable epoxy-amine adduct of claim 1, wherein said dienefunctional mono-isocyanate reactant comprises the reaction product of(a) diisocyanate reactant in approximately one-to-one molar ratio with(b) diene reactant selected from the group consisting of monohydroxyfunctional diene reactant, monoamino functional diene reactant and acompatible mixture of any of them.
 7. The self-crosslinkable epoxy-amineadduct of claim 6, wherein said diisocyanate reactant is selected fromthe group consisting of phenylene diisocyanate, toluene diisocyanate,isophorone diisocyanate, diisocyanatoalkane wherein the alkyl moiety hasabout three to about ten carbons and a compatible mixture of any ofthem.
 8. The self-crosslinkable epoxy-amine adduct of claim 6, whereinsaid diene reactant is selected from the group consisting of furfurylalcohol, furfuryl amine, 2-hydroxymethyl-1,3-butadiene,2-aminomethyl-1,3-butadiene and a compatible mixture of any of them. 9.The self-crosslinkable epoxy-amine adduct of claim 1, wherein saiddieneophile functional mono-isocyanate reactant comprises the reactionproduct of (i) diisocyanate reactant in approximately 1:1 molar ratiowith (ii) dieneophile reactant selected from the group consisting ofmonohydroxy functional dieneophile reactant, monoamino functionaldieneophile reactant and a compatible mixture of any of them.
 10. Theself-crosslinkable epoxy-amine adduct of claim 9, wherein saiddieneophile reactant is selected from the group consisting ofmethylolmaleimide, hydroxypropyl-methacrylate, allyl alcohol, allylamine, hydroxyethyl-methacrylate, hydroxyethylacrylate, and a compatiblemixture of any of them.
 11. The self-crosslinkable epoxy-amine adduct ofclaim 9, wherein said diisocyanate reactant is selected from the groupconsisting of phenylene diisocyanate, toluene diisocyanate, isophoronediisocyanate, diisocyanatoalkane wherein the alkyl moiety has aboutthree to about ten carbons and a compatible mixture of any of them. 12.The self-crosslinkable epoxy-amine adduct of claim 1, wherein at least aportion of said diene-functionalized dieneophile-functionalizedepoxy-amine adduct bears hydroxy functionality, said composition furthercomprising crosslinking agent substantially reactive with hydroxyfunctionality.
 13. The self-crosslinkable epoxy-amine adduct of claim 1adapted for use in coating compositions that retard corrosion ofcorrosion susceptible substrates, further comprising organic solvent,wherein said diene-functionalized dieneophile-functionalized epoxy-amineadduct is of number average molecular weight about 500-5000.
 14. Acrosslinkable composition of matter adapted for use in electrodepositionof coatings on a substrate, which coatings are heat curable, whichcomposition comprises: substantially gel-free conjugateddiene-functionalized dieneophile-functionalized epoxy-amine adduct, atleast partially neutralized with solubilizing acid, comprising thereaction product of:(i) polyhydroxy functional epoxy-amine reactantcomprising the reaction product of polyepoxy reactant having an averageof at least about 2 epoxy groups per molecule, with secondary aminereactant having a total of less than about 20 carbons per aminonitrogen, wherein each hydroxy group, if any, of the secondary amine isremoved at least 1 carbon from each amino nitrogen; with (ii) conjugateddiene functional mono-isocyanate reactant; and with (iii) dieneophilefunctional mono-isocyanate reactant other than said conjugated dienefunctional mono-isocyanate reactantwhich at least partially neutralizeddiene-functionalized dieneophile-functionalized epoxy-amine adduct isdispersed in aqueous solvent.
 15. The crosslinkable composition ofmatter of claim 14, wherein said polyepoxy reactant for said polyhydroxyfunctional epoxy-amine reactants has number average molecular weightabout 700-8000.
 16. The crosslinkable composition of matter of claim 14,wherein said secondary amine reactant for said polyhydroxy functionalepoxy-amine reactant is selected from the group consisting ofdialkylamine, dialkanolamine, N-alkylaniline or a compatible mixture ofany of them, wherein each alkyl moiety and each alkanol moiety has fromone to about ten carbons.
 17. The crosslinkable composition of matter ofclaim 14, wherein said secondary amine reactant for said polyhydroxyfunctional epoxy-amine reactant consists essentially of diethanolamine.18. The crosslinkable composition of matter of claim 14, wherein saiddiene functional mono-isocyanate reactant comprises the reaction productof (a) diisocyanate reactant in approximately 1:1 molar ratio with (b)diene reactant selected from the group consisting of monohydroxyfunctional diene reactant, monoamino functional diene reactant and acompatible mixture of any of them.
 19. The crosslinkable composition ofmatter of claim 18, wherein said diisocyanate reactant is selected fromthe group consisting of phenylene diisocyanate, toluene diisocyanate,isophorone diisocyanate, diisocyanatoalkane wherein the alkyl moiety hasabout three to about ten carbons and a compatible mixture of any ofthem.
 20. The crosslinkable composition of matter of claim 18, whereinsaid diene reactant is selected from the group consisting of furfurylalcohol, furfuryl amine, 2-hydroxymethyl-1,3-butadiene,2-aminomethyl-1,3-butadiene and the like and a compatible mixture of anyof them.
 21. The crosslinkable composition of matter of claim 14,wherein said dieneophile functional mono-isocyanate reactant comprisesthe reaction product of (i) diisocyanate reactant in approximately 1:1molar ratio with (ii) dieneophile reactant selected from the groupconsisting of monohydroxy functional dieneophile reactant, monoaminofunctional dieneophile reactant and a compatible mixture of any of them.22. The crosslinkable composition of matter of claim 21, wherein saiddieneophile reactant is selected from the group consisting ofmethylolmaleimide, hydroxypropyl-methacrylate, allyl alcohol, allylamine, hydroxyethyl-methacrylate, hydroxyethylacrylate and a compatiblemixture of any of them.
 23. The crosslinkable composition of matter ofclaim 21, wherein said diisocyanate reactant is selected from the groupconsisting of phenylene diisocyanate, toluene diicoyanate, isophoronediisocyanate, diisocyanatoalkane wherein the alkyl moiety has aboutthree to about ten carbons and a compatible mixture of any of them. 24.The crosslinkable composition of matter of claim 14, wherein saiddiene-functionalized epoxy-amine adduct and saiddieneophile-functionalized epoxy-amine adduct are each at leastpartially neutralized with organic acid selected from the groupconsisting of acetic acid, lactic acid, formic acid, butyric acid and acompatible mixture of any of them.
 25. The crosslinkable composition ofmatter according to claim 14, wherein at least a portion ofdiene-functionalized dieneophile-functionalized epoxy-amine adduct bearshydroxy functionality, said composition further comprising crosslinkingagent substantially reactive with said hydroxy functionality.
 26. Thecrosslinkable composition of matter of claim 14 further comprising anorganic coupling solvent miscible with water.
 27. The crosslinkablecomposition of matter according to claim 14, wherein saiddiene-functionalized dieneophile-functionalized epoxy-amine adduct is ofnumber average molecular weight about 500-800.
 28. A crosslinkablecomposition of matter adapted for use in electrodeposition of coatingson a substrate, which coatings are heat curable, which compositioncomprises: substantially gel-free diene-functionalizeddieneophile-functionalized epoxy-amine adduct of number averagemolecular weight about 500-8000, at least partially neutralized withsolubilizing acid selected from the group consisting of acetic acid,lactic acid, formic acid, buryric acid and a compatible mixture of anyof them, which diene-functionalized epoxy-amine adduct comprises thereaction product of:(i) polyhydroxy functional epoxy-amine reactantcomprising the reaction product of polyepoxide reactant having anaverage of at least about two epoxy groups per molecule with secondaryamine reactant selected from the group consisting of dialkanolaminewherein each alkanol moiety has about one to three carbons; with (ii)diene functional mono-isocyante reactant comprising the reaction productof (a) diisocyanate reactant selected from the group consisting ofphenylene diisocyanate, toluene diisocyanate, isophorone diisocyanate,diisocyanatoalkane wherein the alkyl moiety has about three to about tencarbons, and a compatible mixture of any of them, with (b) dienereactant selected from the group consisting of furfuryl amine,2-aminomethyl-1,3-butadiene and a compatible mixture of any of them; andwith (iii) dieneophile functional mono-isocyanate reactant comprisingthe reaction product of (a) diisocyanate reactant selected from thegroup consisting of phenylene diisocyanate, toluene diisocyanate,isophorone diisocyanate, diisocyanatoalkane wherein the alkyl moiety hasabout three to about ten carbons, and a compatible mixture of any ofthem, with (b) dieneophile reactant selected from the group consistingof methylolmaleimide, hydroxypropyl-methacrylate, allyl alcohol, allylamine, hydroxyethyl-methacrylate, hydroxyethylacrylate and a compatiblemixture of any of them;which at least partially neutralizeddiene-functionalized dieneophile-functionalized epoxy-amine adduct isdispersed together in aqueous solvent.